The present invention relates to an improved color ink jet printing apparatus. An ink jet printer of the present type generally comprises an ink ejection head for ejecting three primary colors of ink onto a sheet of paper which is moved relative thereto. The ejection head comprises three ink ejectors for the respective colors which eject jets of colored ink in superposition onto the sheet in response to three respective electrical color signals. In other words, each ejector will eject ink as long as the respective signal is applied thereto.
Whereas color ink jet printers are practical and economical, a problem has remained heretofore unsolved. The problem is that erroneous colors are produced at the boundaries of two colors on the sheet, where one of the ejectors is shut off and another of the ejectors is turned on.
Due to lack of immediate absorption by the paper and/or diffusion through the paper fibers, mixing of ink occurs at such boundaries. For example, at a boundary between yellow and cyan printing areas on the sheet, mixing of the two colors of ink will produce a green line. The color green is erroneous since it is not designated by the color signals. Such erroneous colors at boundaries between designated colors substantially degrade the printing quality.